Display device

ABSTRACT

A display device capable of displaying both a 3D image and a 2D image is provided. The display device includes a plurality of optical filter regions where light-blocking panels for producing binocular disparity are arranged in matrix. The light-blocking panel can select whether to transmit light emitted from a display panel in each of the plurality of optical filter regions. Thus, in the display device, some regions where binocular disparity is produced can be provided. Consequently, the display device can display both a 3D image and a 2D image.

TECHNICAL FIELD

The present invention relates to display devices. In particular, thepresent invention relates to display devices capable of displayingthree-dimensional (3D) images.

BACKGROUND ART

The market for 3D display devices is expanding. A difference in retinalimages seen by both eyes (binocular disparity) that occurs when a usersees a 3D object by both eyes is produced in a display device, so that a3D image can be displayed. 3D display devices using such binoculardisparity with a variety of display methods have been developed andcommercialized. Among such display devices, small display devices suchas personal digital assistants or portable game machines mainly adopt adirect-view display method using an optical system such as a parallaxbarrier, a lenticular lens, or a microlens array.

For example, Patent Document 1 discloses a technique for displaying a 3Dimage by a parallax barrier so that a right eye sees an image for theright eye and a left eye sees an image for the left eye.

REFERENCE

Patent Document 1: Japanese Published Patent Application No. 8-036145.

DISCLOSURE OF INVENTION

It is an object of one embodiment of the present invention to provide adisplay device capable of displaying both a 3D image and atwo-dimensional (2D) image.

One embodiment of the present invention is a display device thatincludes a display panel including a plurality of pixel regions arrangedin matrix and a light-blocking panel including a plurality of opticalshutter regions arranged in matrix. The optical shutter region includesa switch and a liquid crystal element whose light transmission isselected depending on a signal input through the switch. Thelight-blocking panel is provided in a direction in which light isemitted from the display panel.

The display panel displays an image by control of alignment of a liquidcrystal. A display device including such a display panel is also oneembodiment of the present invention.

A display device includes a display panel including a plurality of pixelregions arranged in matrix and a light-blocking panel including aplurality of optical shutter regions arranged in matrix. The pixelregion includes a light-emitting element emitting white light by organicelectroluminescence and a color filter for transmitting light in aspecific wavelength range included in the white light emitted from thelight-emitting element and for changing the white light into light witha chromatic color. The optical shutter region includes a switch and aliquid crystal element whose light transmission is selected depending ona signal input through the switch. The light-blocking panel is providedin a direction in which light is emitted from the display panel. Such adisplay device is also one embodiment of the present invention.

A display device includes a display panel including a plurality of pixelregions arranged in matrix and a light-blocking panel including aplurality of optical shutter regions arranged in matrix. The pixelregion includes a light-emitting element emitting light with a chromaticcolor by organic electroluminescence. The optical shutter regionincludes a switch and a liquid crystal element whose light transmissionis selected depending on a signal input through the switch. Thelight-blocking panel is provided in a direction in which light isemitted from the display panel. Such a display device is also oneembodiment of the present invention.

In a display device according to one embodiment of the presentinvention, binocular disparity can be produced by a light-blockingpanel. Further, the light-blocking panel can select whether to transmitlight emitted from a display panel in each of a plurality of opticalfilter regions. Thus, in the display device, some regions wherebinocular disparity is produced can be provided. Consequently, thedisplay device according to one embodiment of the present invention candisplay both a 3D image and a 2D image.

BRIEF DESCRIPTION OF DRAWINGS

In the accompanying drawings:

FIGS. 1A and 1B are schematic diagrams illustrating a structure exampleof a display device;

FIGS. 2A and 2B are schematic diagrams illustrating the operating stateof the display device;

FIGS. 3A to 3C are schematic diagrams illustrating modification examplesof the display device;

FIGS. 4A to 4C are a cross-sectional view and plan views illustrating aspecific example of a pixel region included in the display panel;

FIGS. 5A and 5B are cross-sectional views illustrating a specificexample of a pixel region included in the display panel;

FIGS. 6A and 6B are a plan view and a cross-sectional view illustratinga specific example of an optical shutter region included in alight-blocking panel;

FIGS. 7A and 7B are a plan view and a cross-sectional view illustratinga specific example of an optical shutter region included in thelight-blocking panel;

FIGS. 8A to 8C illustrate specific examples of electronic devices;

FIG. 9A illustrates a structure example of the display device, FIG. 9Bis an equivalent circuit diagram of the optical shutter region in FIGS.6A and 6B and FIGS. 7A and 7B, and FIGS. 9C and 9D are flow chartsillustrating an operation example of a controller;

FIG. 10 illustrates the structure of a display device in Example 3;

FIGS. 11A and 11B illustrate a positional relation between an opticalshutter region and a pixel region in Example 3;

FIGS. 12A and 12B illustrate a positional relation between an opticalshutter region and a pixel region in Example 3;

FIGS. 13A and 13B illustrate a positional relation between an opticalshutter region and a pixel region in Example 3;

FIG. 14 illustrates a display device in Example 4;

FIG. 15 illustrates the display device in Example 4;

FIG. 16 illustrates the display device in Example 4;

FIG. 17 illustrates the display device in Example 4; and

FIG. 18 illustrates a specific example of a light-blocking panel.

BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment and examples of the present invention will be described indetail below with reference to the drawings. Note that the presentinvention is not limited to the following description. It will bereadily appreciated by those skilled in the art that modes and detailsof the present invention can be modified in various ways withoutdeparting from the spirit and scope of the present invention. Thepresent invention therefore should not be construed as being limited tothe following description of the embodiment and the examples.

First, a display device according to one embodiment of the presentinvention is described with reference to FIGS. 1A and 1B and FIGS. 2Aand 2B.

STRUCTURE EXAMPLE OF DISPLAY DEVICE

FIG. 1A is a schematic diagram illustrating a display device accordingto one embodiment of the present invention. The display device in FIG.1A includes a display panel 10 including a plurality of pixel regions100 arranged in matrix and a light-blocking panel 20 including aplurality of optical shutter regions 200 arranged in matrix. Note thatthe light-blocking panel 20 is provided in a direction in which light isemitted from the display panel 10. The light-blocking panel 20 can blockdisplay of an image viewed by a user in each of the plurality of opticalshutter regions 200. Note that here, the light-blocking panel 20 doesnot block display of an image viewed by the user in regions other thanthe plurality of optical shutter regions 200. Further, in FIG. 1A,dotted lines in the light-blocking panel 20 indicate regions onto whichimages in the pixel regions 100 provided in the display panel 10 arefocused.

Note that as the display panel 10 in FIG. 1A, a panel for displayingimages by control of alignment of liquid crystals (such a panel is alsoreferred to as a liquid crystal display device), a panel for displayingimages by organic electroluminescence (also referred to as organic EL)(such a panel is also referred to as an EL display device), or the likecan be used. Further, as the light-blocking panel 20 in FIG. 1A, a panelfor selecting whether to block light by control of alignment of liquidcrystals, a panel for selecting whether to block light with the use of amicro-electro-mechanical systems (MEMS) switch as an optical shutter, orthe like can be used.

FIG. 1B is a schematic diagram illustrating the structure of the displaydevice in FIG. 1A taken along broken line A-B. The optical shutterregion 200 is provided so that one of a left eye 31 and a right eye 32views an image in the specific pixel region 100 directly (without theoptical shutter region 200) and the other of the left eye 31 and theright eye 32 views the image in the specific pixel region 100 throughthe optical shutter region 200 when the user sees the display devicefrom a specific distance. Specifically, the left eye 31 directly viewsan image in a pixel region 100 a and the right eye 32 views the image inthe pixel region 100 a through an optical shutter region 200 a when theuser sees the display device from the specific distance. Thus, a user'seyes can view an image in the pixel region 100 a when display of animage in the pixel region 100 a is not blocked in the optical shutterregion 200 a or only the left eye 31 of the user can view an image inthe pixel region 100 a when display of an image in the pixel region 100a is blocked in the optical shutter region 200 a.

In short, the plurality of optical shutter regions each have a functionof selecting whether the left eye views an image in the specific pixelregion and a function of selecting whether the right eye views an imagein a pixel region adjacent to the specific pixel region. Note that theplurality of optical shutter regions are different in positionalrelation between the optical shutter region and the two pixel regions(the pixel region in which whether an image is viewed by the left eye isselected by the optical shutter and the pixel region in which whether animage is viewed by the right eye is selected by the optical shutter).Specifically, the pixel region 100 a and a pixel region 100 b are pixelregions in which whether an image is viewed by the left eye 31 or theright eye 32 is selected by the optical shutter region 200 a, and apixel region 100 c and a pixel region 100 d are pixel regions in whichwhether an image is viewed by the left eye 31 or the right eye 32 isselected by an optical shutter region 200 b. It is apparent from FIG. 1Bthat the positional relation between the optical shutter region 200 aand the pixel regions 100 a and 100 b is different from the positionalrelation between the optical shutter region 200 b and the pixel regions100 c and 100 d. For example, in FIG. 1B, an arrow starting from asymbol a indicates the center of the pixel region 100 a and the pixelregion 100 b, and an arrow starting from a symbol b indicates the centerof the pixel region 100 c and the pixel region 100 d. It is apparentthat the positional relations are different from the fact that the arrowstarting from the symbol a reaches the optical shutter region 200 a andthe arrow starting from the symbol b does not reach the optical shutterregion 200 b.

Note that in order to display a 3D image to be described later, it isnecessary that the plurality of optical shutter regions be different inpositional relation between the optical shutter region and thecorresponding two pixel regions or that the positional relation betweenan optical shutter region included in a specific region andcorresponding two pixel regions be different from the positionalrelation between an optical shutter region included in a region otherthan the specific region and corresponding two pixel regions, though thepositional relation between the optical shutter region included in thespecific region and the corresponding two pixel regions is common Forexample, it is necessary that the positional relation between an opticalshutter region in the center of a screen and corresponding two pixelregions be different from the positional relation between an opticalshutter region included at an end of the screen and corresponding twopixel regions. Here, the positional relations are changed depending onspecifications (e.g., assumption of a distance of the user's eyes). Notethat in order to display a 3D image, it is necessary that the pitch ofthe optical shutter region (indicated by d1 in FIG. 1B) be smaller thanthe pitch of adjacent two pixel regions (indicated by d2 in FIG. 1B). Inshort, a distance from one end to an opposing end of all the opticalshutter regions provided in the light-blocking panel is shorter than adistance from one end to an opposing end of all the pixel regionsprovided in the display panel.

Note that the meaning of the expression “the positional relation betweenan optical shutter region included in a specific region andcorresponding two pixel regions is different from the positionalrelation between an optical shutter region included in a region otherthan the specific region and corresponding two pixel regions, though thepositional relation between the optical shutter region included in thespecific region and the corresponding two pixel regions is common” inthe above paragraph is as follows. For example, although “the positionalrelation between hundred pairs of an optical shutter region andcorresponding two pixel regions” in the display device is common, thecommon positional relation of the hundred pairs is different from “thepositional relation between a pair of an optical shutter region andcorresponding two pixel regions which is other than the hundred pairs”.

FIG. 2A is a schematic diagram illustrating the specific operating stateof the display device in FIG. 1A. In the operating state in FIG. 2A,among the plurality of pixel regions 100 included in the display panel10, in the pixel region 100 in which the user views an image through aregion 20 a in the light-blocking panel 20, a 3D image (L) for the lefteye or a 3D image (R) for the right eye is displayed, and 2D images aredisplayed in the pixel regions 100 other than the region. Then, displayof an image is blocked in the plurality of optical shutter regions 200in the region 20 a of the light-blocking panel 20, and display of animage is not blocked in regions other than the region 20 a.Specifically, in each of the optical shutter regions 200, display of animage is blocked so that in the two pixel regions 100 adjacent to eachother in a lateral direction (in a direction in which a parallax betweenthe left eye and the right eye of the user exists), the right eye 32 ofthe user does not view an image in the pixel region 100 that is providedon a left side and displays a 3D image (L) for the left eye, and theleft eye 31 of the user does not view an image in the pixel region 100that is provided on a right side and displays a 3D image (R) for theright eye. Thus, a 3D image can be displayed in the specific region (theregion 20 a). Consequently, the display device according to oneembodiment of the present invention can display both a 3D image in theregion 20 a and 2D images in regions other than the region 20 a (seeFIG. 2B).

MODIFICATION EXAMPLE OF DISPLAY DEVICE

The display device according to one embodiment of the present inventionis not limited to the display device in FIG. 1A. For example, any ofdisplay devices in FIGS. 3A to 3C can be used as the display deviceaccording to one embodiment of the present invention.

The display device in FIG. 3A differs from the display device in FIG. 1Ain that optical filter regions in the light-blocking panel 20 arearranged in a stripe pattern. Further, the operating state of thedisplay device in FIG. 3A differs from the operating state of thedisplay device in FIG. 2A in that when the display device in FIG. 3Adisplays a 3D image, a 3D image (L) for the left eye or a 3D image (R)for the right eye is displayed on the display panel 10 per column in aplurality of pixel regions arranged in matrix.

The display device in FIG. 3B differs from the display device in FIG. 1Ain that a plurality of pixel regions in the display panel 10 arearranged in a delta pattern.

The display device in FIG. 3C differs from the display device in FIG. 1Ain that optical shutter regions whose number is the same orsubstantially the same as the number of optical shutter regions in thepixel region 100 of the display panel 10 are provided in thelight-blocking panel 20. In the display device in FIG. 3C, the displaypanel 10 can display an image only in the pixel region 100 that existsin a specific region. Thus, as compared to the display device in FIG.1A, crosstalk during display of a 3D image can be reduced.

FIRST SPECIFIC EXAMPLE OF DISPLAY PANEL 10

A specific example of the display panel 10 is described with referenceto FIGS. 4A to 4C. Note that FIG. 4A is a cross-sectional view of thepixel region 100 that includes a light-emitting element emitting whitelight by organic electroluminescence and a color filter that transmitslight in a specific wavelength range included in the white light emittedfrom the light-emitting element and changes the white light into lightwith a chromatic color. FIGS. 4B and 4C are plan views of the pixelregion 100 in FIG. 4A.

The display panel in FIG. 4A emits light (displays an image) in adirection indicated by arrows in FIG. 4A. That is, the display panel hasa so-called top-emission structure in which light is emitted not througha first substrate 201 provided with a light-emitting layer 218 butthrough a second substrate 251. Note that the light-emitting layer 218emits white light by organic electroluminescence.

FIG. 4B is a plan view of the first substrate 201 seen from atransflective electrode layer 219 side, and FIG. 4C is a plan view ofthe second substrate 251 seen from a light-blocking film 252 side. Notethat FIG. 4A is a cross-sectional view taken along broken line A1-A2 inFIGS. 4B and 4C. In the plan views in FIGS. 4B and 4C, some components(e.g., the light-emitting layer 218) are not illustrated in order toavoid complex views.

As illustrated in FIG. 4A, a blue pixel 240 a, a green pixel 240 b, anda red pixel 240 c are provided between the first substrate 201 and thesecond substrate 251. Further, a transistor 230 for controlling drive ofthe light-emitting element and a reflective electrode layer 214 that iselectrically connected to the transistor 230 are provided over the firstsubstrate 201.

Note that here, the blue pixel 240 a includes a light-emitting elementthat has emission intensity in a blue region, the green pixel 240 bincludes a light-emitting element that has emission intensity in a greenregion, and the red pixel 240 c includes a light-emitting element thathas emission intensity in a red region. These light-emitting elementsfunction as micro-cavities to intensify desired emission spectra.

In the blue pixel 240 a, the light-emitting layer 218 is directly formedon the reflective electrode layer 214 as the light-emitting element thathas emission intensity in the blue region, and the transflectiveelectrode layer 219 is formed over the light-emitting layer 218.

In the green pixel 240 b, a first transparent electrode layer 220 a isformed over the reflective electrode layer 214 as the light-emittingelement that has emission intensity in the green region, thelight-emitting layer 218 is formed over the first transparent electrodelayer 220 a, and the transflective electrode layer 219 is formed overthe light-emitting layer 218.

In the red pixel 240 c, a second transparent electrode layer 220 b isformed over the reflective electrode layer 214 as the light-emittingelement that has emission intensity in the red region, thelight-emitting layer 218 is formed over the second transparent electrodelayer 220 b, and the transflective electrode layer 219 is formed overthe light-emitting layer 218.

In this manner, the light-emitting elements of the pixels (the bluepixel 240 a, the green pixel 240 b, and the red pixel 240 c) aredifferent in structure between the reflective electrode layer 214 andthe transflective electrode layer 219.

The second substrate 251 is provided with a light-blocking film 252 thatfunctions as a black matrix, a color filter 254, and an overcoat 256.The color filter 254 is a colored layer, which transmits light of colors(blue, green, and red) emitted from the light-emitting elements andemits light from the light-emitting layer 218 to a second substrate 251side.

In this manner, it can be said that the light-emitting elements of thepixels (the blue pixel 240 a, the green pixel 240 b, and the red pixel240 c) are different in optical distance when the optical path lengthbetween the reflective electrode layer 214 and the transflectiveelectrode layer 219 is changed. This optical distance may be opticalpath length with which a spectrum needed for the light-emitting elementof each pixel is amplified by a resonance effect. Only in thelight-emitting element that has emission intensity in the blue regionprovided in the blue pixel 240 a, the light-emitting layer 218 isdirectly formed on the reflective electrode layer 214 and thetransflective electrode layer 219 is formed over the light-emittinglayer 218. In other words, transparent electrode layers (the firsttransparent electrode layer 220 a and the second transparent electrodelayer 220 b) are not formed.

With such a structure, a transparent electrode layer to be formed in theblue pixel 240 a is not needed; thus, the number of steps and cost canbe reduced.

Note that there is no particular limitation on a space 260 between thefirst substrate 201 and the second substrate 251 as long as the space260 transmits light. It is preferable that the space 260 be filled witha light-transmitting material whose refractive index is higher than thatof the air. In the case where the refractive index is low, light emittedfrom the light-emitting layer 218 in an oblique direction is furtherrefracted by the space 260, and light is emitted from an adjacent pixelin some cases. Thus, for example, the space 260 can be filled with alight-transmitting adhesive having high refractive index and capable ofbonding the first substrate 201 and the second substrate 251 to eachother. Alternatively, an inert gas such as nitrogen or argon or the likecan be used.

Next, the details of the display panel in FIGS. 4A to 4C and a methodfor manufacturing the display panel are described.

First, a method for forming the first substrate 201 provided with thetransistor 230 for controlling drive of the light-emitting element, thelight-emitting layer 218, and the like is described below.

A conductive layer is formed over the first substrate 201 having aninsulating surface, and then, a first photolithography process isperformed so that a resist mask is formed. An unnecessary portion of theconductive layer is etched away, so that a gate electrode layer 202 isformed. Etching is preferably performed so that end portions of the gateelectrode layer 202 are tapered as illustrated in FIG. 4A becausecoverage with a film stacked thereover is improved.

Although there is no particular limitation on a substrate which can beused as the first substrate 201, it is necessary that the substrate haveat least heat resistance high enough to withstand heat treatment to beperformed later. For example, a glass substrate can be used as the firstsubstrate 201.

In the case where the temperature of the heat treatment to be performedlater is high, a glass substrate whose strain point is 730° C. or higheris preferably used as the glass substrate. For the glass substrate, aglass material such as aluminosilicate glass, aluminoborosilicate glass,or barium borosilicate glass is used, for example. Note that in general,by containing more barium oxide (BaO) than boron oxide (B₂O₃), a morepractical heat-resistant glass substrate can be obtained. Thus, a glasssubstrate containing more BaO than B₂O₃ is preferably used.

Note that instead of the glass substrate, a substrate formed using aninsulator, such as a ceramic substrate, a quartz substrate, or asapphire substrate, may be used. Alternatively, crystallized glass orthe like can be used. The display panel has a top-emission structure inwhich light is extracted through the second substrate 251; thus, anon-light-transmitting substrate such as a metal substrate can be usedas the first substrate 201.

An insulating film which serves as a base film may be provided betweenthe first substrate 201 and the gate electrode layer 202. The base filmhas a function of preventing diffusion of an impurity element from thefirst substrate 201, and can be formed to have a single-layer structureor a layered structure using one or more films selected from a siliconnitride film, a silicon oxide film, a silicon nitride oxide film, and asilicon oxynitride film.

The gate electrode layer 202 can be formed to have a single-layerstructure or a layered structure using a metal material such asmolybdenum, titanium, chromium, tantalum, tungsten, aluminum, copper,neodymium, or scandium, or an alloy material containing any of thesemetal materials as a main component.

Next, a gate insulating layer 204 is formed over the gate electrodelayer 202. The gate insulating layer 402 can be formed to have asingle-layer structure or a layered structure including a silicon oxidelayer, a silicon nitride layer, a silicon oxynitride layer, a siliconnitride oxide layer, or an aluminum oxide layer by plasma-enhanced CVD,sputtering, or the like. For example, a silicon oxynitride film may beformed using SiH₄ and N₂O as a deposition gas by plasma-enhanced CVD.

Next, a semiconductor layer is formed, and an island-shapedsemiconductor layer 206 is formed through a second photolithographyprocess.

The semiconductor layer 206 can be formed using a silicon semiconductoror an oxide semiconductor. Single crystal silicon, polycrystallinesilicon, microcrystalline silicon, amorphous silicon, or the like can beused as the silicon semiconductor. A four-component metal oxide such asan In—Sn—Ga—Zn—O-based oxide semiconductor; a three-component metaloxide such as an In—Ga—Zn—O-based oxide semiconductor, anIn—Sn—Zn—O-based oxide semiconductor, an In—Al—Zn—O-based oxidesemiconductor, a Sn—Ga—Zn—O-based oxide semiconductor, anAl—Ga—Zn—O-based oxide semiconductor, or a Sn—Al—Zn—O-based oxidesemiconductor; a two-component metal oxide such as an In—Zn—O-basedoxide semiconductor, a Sn—Zn—O-based oxide semiconductor, anAl—Zn—O-based oxide semiconductor, a Zn—Mg—O-based oxide semiconductor,a Sn—Mg—O-based oxide semiconductor, an In—Mg—O-based oxidesemiconductor, or an In—Ga—O-based oxide semiconductor; asingle-component metal oxide such as an In—O-based oxide semiconductor,a Sn—O-based oxide semiconductor, or a Zn—O-based oxide semiconductor;or the like can be used as the oxide semiconductor. Note that in thisspecification, for example, an In—Sn—Ga—Zn—O-based oxide semiconductoris a metal oxide containing indium (In), tin (Sn), gallium (Ga), andzinc (Zn), and there is no particular limitation on the stoichiometricproportion thereof. The oxide semiconductor may contain silicon. Anoxide semiconductor which is an In—Ga—Zn—O-based metal oxide ispreferably used as the semiconductor layer 206 so that the semiconductorlayer has low off-state current because leakage current in an off statecan be reduced.

Next, a conductive film is formed over the gate insulating layer 204 andthe semiconductor layer 206, and a source and drain electrode layers 208are formed through a third photolithography process.

As the conductive film used for the source and drain electrode layers208, for example, a metal film including an element selected from Al,Cr, Cu, Ta, Ti, Mo, or W, a metal nitride film including the aboveelement as its component (e.g., a titanium nitride film, a molybdenumnitride film, or a tungsten nitride film), or the like can be used.Alternatively, a film of a high-melting-point metal such as Ti, Mo, or Wor a metal nitride film thereof (e.g., a titanium nitride film, amolybdenum nitride film, or a tungsten nitride film) may be formed overor/and below a metal film of Al, Cu, or the like. Alternatively, theconductive film used for the source and drain electrode layers 208 maybe formed using a conductive metal oxide. Indium oxide (In₂O₃), tinoxide (SnO₂), zinc oxide (ZnO), ITO, an alloy of indium oxide and zincoxide (In₂O₃—ZnO), or any of these metal oxide materials containingsilicon oxide can be used as the conductive metal oxide.

Next, an insulating layer 210 is formed over the semiconductor layer 206and the source and drain electrode layers 208. An inorganic insulatingfilm such as a silicon oxide film or a silicon oxynitride film can beused as the insulating layer 210.

Then, an insulating layer 212 is formed over the insulating layer 210.

As the insulating layer 212, an insulating film with a planarizationfunction is preferably selected in order to reduce surface unevennessdue to the transistor. For example, an organic material such aspolyimide, acrylic, or benzocyclobutene can be used. Other than suchorganic materials, a low-dielectric constant material (a low-k material)or the like can be used. Note that the insulating layer 212 may beformed by a stack of a plurality of insulating films formed using thesematerials.

Next, an opening which reaches the source and drain electrode layers 208is formed in the insulating layer 212 and the insulating layer 210through a fourth photolithography process. As a method for forming theopening, dry etching, wet etching, or the like may be selected asappropriate.

Next, a conductive film is formed over the insulating layer 212 and thesource and drain electrode layers 208, and a reflective electrode layer214 is formed through a fifth photolithography process.

For the reflective electrode layer 214, a material which efficientlyreflects light emitted from the light-emitting layer 218 is preferablyused because light extraction efficiency can be improved. Note that thereflective electrode layer 214 may have a layered structure. Forexample, a conductive film of a metal oxide, titanium, or the like canbe formed thin on a side which is in contact with the light-emittinglayer 218, and a metal film with high reflectance (a film of aluminum,an alloy containing aluminum, silver, or the like) can be used on a sideopposite to the side which is in contact with the light-emitting layer218. Such a structure is preferable because formation of an insulatingfilm between the light-emitting layer 218 and the metal film with highreflectance (the film of aluminum, an alloy containing aluminum, silver,or the like) can be suppressed.

Next, a transparent conductive film is formed over the reflectiveelectrode layer 214, and the first transparent electrode layer 220 a isformed through a sixth photolithography process.

Then, a transparent conductive film is formed over the reflectiveelectrode layer 214 and the first transparent electrode layer 220 a, andthe second transparent electrode layer 220 b is formed through a seventhphotolithography process. Note that only in the blue pixel 240 a, thefirst transparent electrode layer and the second transparent electrodelayer are not formed.

Indium oxide (In₂O₃), tin oxide (5nO₂), zinc oxide (ZnO), ITO, an alloyof indium oxide and zinc oxide (In₂O₃—ZnO), or any of these metal oxidematerials containing silicon oxide can be used as a material which canbe used for the first transparent electrode layer 220 a and the secondtransparent electrode layer 220 b.

Note that the method for forming the first transparent electrode layer220 a and the second transparent electrode layer 220 b is not limitedthereto. For example, a method can be used by which a transparentconductive film that has thickness needed for the second transparentelectrode layer 220 b is formed, only a portion to be the firsttransparent electrode layer 220 a is subjected to dry etching, wetetching, or the like, and the transparent conductive film is removed toa thickness needed for the first transparent electrode layer 220 a.Further, the second transparent electrode layer 220 b may have a layeredstructure with the transparent conductive film used for the firsttransparent electrode layer 220 a.

With the structure in which the transparent electrode layer is notformed only in the blue pixel 240 a as described above, the number ofmasks can be reduced, and cost can be reduced by a reduction of anunnecessary step.

Then, a partition 216 is formed over the reflective electrode layer 214,the first transparent electrode layer 220 a, and the second transparentelectrode layer 220 b.

The partition 216 is formed using an organic insulating material or aninorganic insulating material. It is particularly preferable that thepartition 216 be formed using a photosensitive resin material to have anopening over the reflective electrode layer 214 in the blue pixel 240 a,an opening over the first transparent electrode layer 220 a in the greenpixel 240 b, and an opening over the second transparent electrode layer220 b in the red pixel 240 c so that sidewalls of the openings havetilted surfaces with continuous curvature.

Then, the light-emitting layer 218 is formed over the reflectiveelectrode layer 214, the first transparent electrode layer 220 a, thesecond transparent electrode layer 220 b, and the partition 216. Thelight-emitting layer 218 may have either a single-layer structure or alayered structure, and it is preferable that light emitted from thelight-emitting layer 218 be light having a peak in each of red, green,and blue wavelength regions.

Next, the transflective electrode layer 219 is formed over thelight-emitting layer 218.

Note that one of the reflective electrode layer 214 and thetransflective electrode layer 219 functions as an anode of thelight-emitting layer 218, and the other of the reflective electrodelayer 214 and the transflective electrode layer 219 functions as acathode of the light-emitting layer 218. It is preferable to use asubstance having a high work function for the electrode layer whichfunctions as an anode, and a substance having a low work function forthe electrode layer which functions as a cathode.

Through the above steps, the first substrate 201 provided with thetransistor 230 for controlling drive of the light-emitting element andthe light-emitting layer 218 is formed.

Next, a method for forming the second substrate 251 provided with thelight-blocking film 252, the color filter 254, and the overcoat 256 isdescribed below.

First, a conductive film is formed on the second substrate 251, and thelight-blocking film 252 is formed through an eighth photolithographyprocess. The light-blocking film 252 can prevent color mixing among thepixels. Note that the light-blocking film 252 is not necessarilyprovided.

A metal film with low reflectance of titanium, chromium, or the like, anorganic resin film impregnated with a black pigment or a black dye, orthe like can be used as the light-blocking film 252.

Then, the color filter 254 is formed on the second substrate 251 and thelight-blocking film 252.

The color filter 254 is a colored layer for transmitting light in aspecific wavelength range. For example, a red (R) color filter fortransmitting light in a red wavelength range, a green (G) color filterfor transmitting light in a green wavelength range, a blue (B) colorfilter for transmitting light in a blue wavelength range, or the likecan be used. Each color filter is formed in a desired position with aknown material by a printing method, an inkjet method, etching using aphotolithography technique, or the like.

Here, a method of using three colors of R, G, and B is described;however, this embodiment is not limited thereto. A structure in whichfour colors of R, G, B, and Y (yellow) are used or a structure in whichfive or more colors are used may be employed.

Next, the overcoat 256 is formed on the light-blocking film 252 and thecolor filter 254. The overcoat 256 can be formed using an organic resinfilm of acrylic, polyimide, or the like. The overcoat 256 can prevent animpurity component or the like contained in the color filter 254 fromdiffusing into a light-emitting layer 218 side. Further, the overcoat256 may have a layered structure of an organic resin film and aninorganic film. Silicon nitride, silicon oxide, or the like can be usedfor the inorganic insulating film. Note that it is possible not toprovide the overcoat 256.

Through the above steps, the second substrate 251 provided with thelight-blocking film 252, the color filter 254, and the overcoat 256 isformed.

Further, the first substrate 201 and the second substrate 251 arealigned and attached to each other to be the display panel. There is noparticular limitation on the method for attaching the first substrate201 and the second substrate 251 to each other, and the first substrate201 and the second substrate 251 can be attached to each other with alight-transmitting adhesive whose refractive index is high, for example.

As described above, in the display panel, the optical distance ischanged between the light-emitting element and the blue pixel includingthe light-emitting element that has emission intensity in the blueregion, the green pixel including the light-emitting element that hasemission intensity in the green region, and the red pixel including thelight-emitting element that has emission intensity in the red region.When a desired spectrum is intensified by a micro-cavity in eachlight-emitting element, a display panel with high color purity can beobtained. Further, since only the blue pixel including thelight-emitting element that emits light of a blue wavelength does notinclude the transparent electrode layer, the number of steps and costcan be reduced.

Note that here, the display panel that has a top-emission (TE) structurein which a light-emitting element emitting white light and a colorfilter (CF) are used in combination (hereinafter abbreviated as awhite+CF+TE structure) is described; however, a display panel that has atop-emission structure in which light-emitting elements are formed by aseparate coloring method (hereinafter referred to as a separatecoloring+TE structure) can be used as the display panel. The separatecoloring method is a method for separately coloring R, G, and Bmaterials in pixels by vapor deposition or the like.

Here, comparison between the display panel with the white+CF+TEstructure and the display panel with the separate coloring+TE structureis described below.

First, in the white+CF+TE structure, coloring is performed using a colorfilter; thus, a color filter is needed. In contrast, in the separatecoloring+TE structure, coloring is performed by separately coloringpixels by vapor deposition or the like; thus, a color filter is notneeded. Consequently, in the separate coloring+TE structure, lightemission at high luminance or low-power drive is possible.

Note that although the white+CF+TE structure needs a color filter, theseparate coloring+TE structure needs a metal mask or the like forseparate coloring. Separate coloring can be performed by an inkjetmethod or the like without a metal mask; however, it is difficult toemploy such a method because of many technical problems. In the casewhere a metal mask is used, a vapor deposition material is alsodeposited on the metal mask; thus, material use efficiency is low andcost is high. Further, the metal mask is in contact with thelight-emitting element, so that yield is decreased because of damage tothe light-emitting element or generation of a scratch, a particle, orthe like due to contact. Consequently, the white+CF+TE structure isbetter in terms of manufacturing cost or productivity.

In addition, it is possible to eliminate a polarizing plate from thewhite+CF+TE structure. In contrast, the separate coloring+TE structureneeds a polarizing plate. An improvement in color purity by using amicro-cavity can be achieved in both the white+CF+TE structure and theseparate coloring+TE structure.

In the separate coloring+TE structure, it is necessary to separatelycolor the pixels and to provide a region necessary for separate coloringbetween the pixels; thus, the size of one pixel cannot be increased.Consequently, the aperture ratio is markedly decreased. In contrast, inthe white+CF+TE structure, it is not necessary to provide a regionnecessary for separate coloring between the pixels; thus, the size ofone pixel can be increased. Consequently, the aperture ratio can beimproved.

In the case where the display panel is made large, a technique formanufacturing the display panel without problems is essential. It isdifficult to employ the separate coloring+TE structure because a metalmask is needed for separate coloring and a technique of a metal mask andproduction equipment that are compatible with a large display panel arenot established. Even if the technique of a metal mask and theproduction equipment that are compatible with a large display panel areestablished, the problem of material use efficiency, i.e., the fact thata vapor deposition material is also deposited on a metal mask, is notsolved. In contrast, the white+CF+TE structure is preferable because ametal mask is not needed and manufacturing can be performed usingconventional production equipment.

An apparatus for manufacturing a display panel greatly influence theproductivity of a display panel. For example, in the case where alight-emitting element has a layered structure of a plurality of films,it is preferable that the apparatus for manufacturing a display panel bean in-line apparatus or a multi-chamber apparatus and that a pluralityof vapor deposition sources be formed on a substrate once orsuccessively. In the separate coloring+TE structure, it is necessary toseparately color pixels and to manufacture the display panel whilereplacing metal masks so that the pixels are formed in desiredpositions. Since metal masks are replaced, it is difficult to use anin-line manufacturing apparatus or a multi-chamber manufacturingapparatus. In contrast, in the white+CF+TE structure, it is easy to usean in-line manufacturing apparatus or a multi-chamber manufacturingapparatus because a metal mask is not needed.

SECOND SPECIFIC EXAMPLE OF DISPLAY PANEL 10

A specific example of the display panel 10 that is different from thespecific example of the display panel 10 in FIGS. 4A to 4C is describedwith reference to FIGS. 5A and 5B. Note that FIGS. 5A and 5B arecross-sectional views of the pixel region 100 that includes thelight-emitting element emitting white light by organicelectroluminescence and the color filter that transmits light in aspecific wavelength range included in the white light emitted from thelight-emitting element and changes the white light into light with achromatic color.

Although the display panel 10 in FIGS. 4A to 4C has a top-emissionstructure in which light is extracted from a surface that is opposite tothe substrate provided with the transistor and the light-emittingelement, a display panel with a bottom-emission structure is describedbelow.

The display panel 10 with a bottom-emission structure is described withreference to FIG. 5A.

In FIG. 5A, a first substrate 300, a second substrate 350, a transistor330 and a light-emitting element 320 that are held between the firstsubstrate 300 and the second substrate 350, and a color filter 354provided on a display surface (a surface to which light from thelight-emitting element 320 is emitted) side of the first substrate 300are included.

Although there is no particular limitation on a substrate which can beused as the first substrate 300, it is necessary that the substrate haveat least heat resistance high enough to withstand heat treatment to beperformed later. For example, a glass substrate can be used as the firstsubstrate 300.

In the case where the temperature of the heat treatment to be performedlater is high, a glass substrate whose strain point is 730° C. or higheris preferably used as the glass substrate. For the glass substrate, aglass material such as aluminosilicate glass, aluminoborosilicate glass,or barium borosilicate glass is used, for example. Note that in general,by containing more barium oxide (BaO) than boron oxide (B₂O₃), a morepractical heat-resistant glass substrate can be obtained. Thus, a glasssubstrate containing more BaO than B₂O₃ is preferably used.

The transistor 330 can be formed in a manner similar to that of thetransistor 230 in FIG. 4A.

The light-emitting element 320 is formed over an insulating layer 310and a partition 312 that are formed over the transistor 330. Alight-emitting layer 316 and a second electrode 318 are sequentiallystacked over a first electrode 314 that is electrically connected to thetransistor 330.

For the insulating layer 310, a material that can flatten unevenness dueto the transistor 330 is preferably used. A material that can transmitlight from the light-emitting element 320 is preferably used. Forexample, an acrylic resin having a high light-transmitting property canbe used for the insulating layer 310. An organic resin film ofpolyimide, acrylic, polyamide, epoxy, or the like, an inorganicinsulating film, or organic polysiloxane can be used for the partition312.

A conductive film which transmits visible light is used as the firstelectrode 314. Indium oxide (In₂O₃), tin oxide (SnO₂), zinc oxide (ZnO),ITO, an alloy of indium oxide and zinc oxide (In₂O₃—ZnO), or any ofthese metal oxide materials containing silicon oxide can be used as theconductive film which transmits visible light, for example.Alternatively, a metal thin film having thickness small enough totransmit light (preferably, approximately 1 to 30 nm) can be used.

The light-emitting layer 316 can be formed in a manner similar to thatof the light-emitting layer 218 in FIG. 4A.

For the second electrode 318, a material which efficiently reflectslight emitted from the light-emitting layer 316 is preferably usedbecause light extraction efficiency can be improved. Note that thesecond electrode 318 may have a layered structure. For example, for thesecond electrode 318, a conductive film of a metal oxide, titanium, orthe like can be formed thin on a side which is in contact with thelight-emitting layer 316 that contains a light-emitting substance, and ametal film with high reflectance (a film of aluminum, an alloycontaining aluminum, silver, or the like) can be used on a side oppositeto the side which is in contact with the light-emitting layer 316. Sucha structure is preferable because formation of an insulating filmbetween the light-emitting layer 316 and the metal film with highreflectance can be suppressed.

Any material can be used for the second substrate 350 as long as it canencapsulate the light-emitting element 320 and a transistor 330.Further, since the light-emitting device in FIG. 5A has thebottom-emission structure, a non-light-transmitting substrate may beused. For example, a glass substrate, a metal substrate, or the like canbe used as appropriate as the second substrate 350.

A space 322 can be formed using a material and a method which aresimilar to those of the space 260. Further, a desiccant that can removemoisture or the like entering the light-emitting element 320 may beencapsulated in the space 322.

On a surface of the first substrate 300 to which light is emitted, thelight-blocking film 352 functioning as a black matrix, a color filter354, and an overcoat 356 are provided. The color filter 354 is a coloredlayer and changes white light emitted from each light-emitting elementinto light with a chromatic color (e.g., blue, green, or red).

In the display panel 10 according to one embodiment of the presentinvention, the color filter 354 and the overcoat 356 can be held betweenthe first substrate 300 and the second substrate 350 (see FIG. 5B).

FIRST SPECIFIC EXAMPLE OF LIGHT-BLOCKING PANEL 20

A specific example of the light-blocking panel 20 is described withreference to FIGS. 6A and 6B. Note that FIG. 6A is a plan view of anoptical shutter region that includes a transistor and a liquid crystalelement to which a signal is input through the transistor, and FIG. 6Bis a cross-sectional view of the optical shutter region in FIG. 6A takenalong broken line A1-A2 and broken line B1-B2. In the optical shutterregion in FIG. 6A, voltage to be applied to the liquid crystal elementdepends on a signal to be input through the transistor. Thus, bycontrolling alignment of liquid crystals included in the liquid crystalelement depending on the signal, whether the optical shutter regiontransmits light is selected. Note that in the display device accordingto one embodiment of the present invention, the transistor can bereplaced with an element that functions as a switch. In other words, inthe optical shutter region, any element can be provided as long as itfunctions as a switch. For example, the transistor can be replaced witha MEMS switch, a relay switch, or the like.

In the optical shutter region in FIGS. 6A and 6B, a conductive layer 501functions as a gate electrode of a transistor 107. Further, a conductivelayer 502 functions as one of a source and a drain of the transistor107. A conductive layer 503 functions as one electrode of a capacitor108. A conductive layer 504 functions as the other of the source and thedrain of the transistor 107 or the other electrode of the capacitor 108.

A gate insulating layer 506 is formed over the conductive layer 501 andthe conductive layer 503. A semiconductor layer 507 of the transistor107 is formed over the gate insulating layer 506 to overlap with theconductive layer 501.

In the optical shutter region in FIGS. 6A and 6B, the gate insulatinglayer 506 and a semiconductor layer 520 are provided in a portion wherethe conductive layer 503 and the conductive layer 502 overlap with eachother. Specifically, the gate insulating layer 506 is provided over theconductive layer 503, the semiconductor layer 520 is provided over thegate insulating layer 506, and the conductive layer 502 is provided overthe semiconductor layer 520. When the semiconductor layer 520 isprovided between the conductive layer 502 and the conductive layer 503,parasitic capacitance between the conductive layer 502 and theconductive layer 503 can be reduced.

In the optical shutter region in FIG. 6A, the gate insulating layer 506and a semiconductor layer 523 are provided in a portion where theconductive layer 501 and the conductive layer 502 overlap with eachother. Specifically, the gate insulating layer 506 is provided over theconductive layer 501, the semiconductor layer 523 is provided over thegate insulating layer 506, and the conductive layer 502 is provided overthe semiconductor layer 523. When the semiconductor layer 523 isprovided between the conductive layer 501 and the conductive layer 502,parasitic capacitance between the conductive layer 501 and theconductive layer 502 can be reduced.

Note that the conductive layer 501 and the conductive layer 503 can beformed by processing one conductive film formed over a substrate 500having an insulating surface into a desired shape. The semiconductorlayer 507, the semiconductor layer 520, and the semiconductor layer 523can be formed by processing one semiconductor film formed over the gateinsulating layer 506 into a desired shape. The conductive layer 502 andthe conductive layer 504 can be formed by processing one conductive filmformed over the gate insulating layer 506, the semiconductor layer 507,the semiconductor layer 520, and the semiconductor layer 523 into adesired shape.

In addition, in the optical shutter region in FIGS. 6A and 6B, aninsulating layer 512 is formed to cover the semiconductor layer 507, thesemiconductor layer 520, the semiconductor layer 523, the conductivelayer 502, and the conductive layer 504. Further, a conductive layer 521is formed over the insulating layer 512 to be in contact with theconductive layer 504 through a contact hole formed in the insulatinglayer 512. An insulating layer 513 is formed over the conductive layer521 and the insulating layer 512. An electrode 505 is formed over theinsulating layer 513. The conductive layer 521 and the electrode 505 arein contact with each other through a contact hole formed in theinsulating layer 513.

Note that although the conductive layer 504 and the electrode 505 are incontact with each other through the conductive layer 521 in the opticalshutter region in FIGS. 6A and 6B, in one embodiment of the presentinvention, the conductive layer 504 and the electrode 505 may be incontact with each other without provision of the conductive layer 521.

A portion where the conductive layer 503 and the conductive layer 504overlap with each other with the gate insulating layer 506 providedtherebetween functions as the capacitor 108.

In FIG. 6B, a spacer 510 is formed over the electrode 505 in a portionwhere the conductive layer 521 and the electrode 505 overlap with eachother.

FIG. 6A is a top view of the pixel provided with the spacer 510. In FIG.6B, a substrate 514 is provided to face the substrate 500 provided withthe spacer 510.

An electrode 515 is provided for the substrate 514, and a liquid crystallayer 516 containing a liquid crystal is provided between the electrode505 and the electrode 515. A liquid crystal element 106 is formed in aportion where the electrode 505, the electrode 515, and the liquidcrystal layer 516 overlap with each other.

Polarizing plates (not illustrated) are provided outside the substrate500 and the substrate 514.

Each of the electrode 505 and the electrode 515 can be formed using alight-transmitting conductive material such as indium tin oxidecontaining silicon oxide (ITSO), indium tin oxide (ITO), zinc oxide(ZnO), indium zinc oxide, or zinc oxide to which gallium is added (GZO),for example.

An alignment film may be provided as appropriate between the electrode505 and the liquid crystal layer 516 or between the electrode 515 andthe liquid crystal layer 516. The alignment film can be formed using anorganic resin such as polyimide or poly(vinyl alcohol). Alignmenttreatment for aligning liquid crystal molecules in a certain direction,such as rubbing, is performed on a surface of the alignment film. Aroller wrapped with cloth of nylon or the like is rolled while being incontact with the alignment film so that the surface of the alignmentfilm can be rubbed in a certain direction. Note that it is also possibleto form the alignment film that has alignment characteristics with theuse of an inorganic material such as silicon oxide by vapor deposition,without alignment treatment.

Injection of liquid crystals for formation of the liquid crystal layer516 may be performed by a dispenser method (a dripping method) or adipping method (a pumping method).

Note that the substrate 514 is provided with a light-blocking film 517capable of blocking light so that disclination caused by disorder ofalignment of the liquid crystal between optical shutter regions isprevented from being observed or dispersed light is prevented fromentering a plurality of adjacent optical shutter regions. Thelight-blocking film 517 can be formed using an organic resin containinga black pigment such as a carbon black or low-valent titanium oxide.Alternatively, the light-blocking film 517 can be formed using a filmincluding chromium.

SECOND SPECIFIC EXAMPLE OF LIGHT-BLOCKING PANEL 20

A specific example of the light-blocking panel 20 that is different fromthe specific example of the light-blocking panel 20 in FIGS. 6A and 6Bis described with reference to FIGS. 7A and 7B. Specifically, an exampleof a light-blocking panel provided with an optical shutter regionincluding a liquid crystal element whose pair of electrodes is formedover one substrate, such as an IPS liquid crystal element or ablue-phase liquid crystal element, is described.

FIG. 7A is an example of the top view of the pixel. FIG. 7B is across-sectional view taken along broken line C1-C2 in FIG. 7A.

In the pixel in FIGS. 7A and 7B, a conductive layer 601 functions as thegate electrode of the transistor 107. Further, a conductive layer 602functions as one of the source and the drain of the transistor 107. Aconductive layer 603 functions as one electrode of the capacitor 108. Aconductive layer 604 functions as the other of the source and the drainof the transistor 107 or the other electrode of the capacitor 108.

A gate insulating layer 606 is formed over the conductive layer 601 andthe conductive layer 603. A semiconductor layer 607 of the transistor107 is formed over the gate insulating layer 606 to overlap with theconductive layer 601. Further, an insulating layer 612 and an insulatinglayer 613 are sequentially formed to cover the semiconductor layer 607,the conductive layer 602, and the conductive layer 604. An electrode 605and an electrode 608 are formed over the insulating layer 613. Theconductive layer 604 and the electrode 605 are connected to each otherthrough a contact hole formed in the insulating layer 612 and theinsulating layer 613.

The conductive layer 601 and the conductive layer 603 can be formed byprocessing one conductive film formed over a substrate 600 having aninsulating surface into a desired shape. The gate insulating layer 606is formed over the conductive layer 601 and the conductive layer 603.The conductive layer 602 and the conductive layer 604 can be formed byprocessing one conductive film formed over the semiconductor layer 607and the gate insulating layer 606 into a desired shape.

A portion where the conductive layer 603 and the conductive layer 604overlap with each other with the gate insulating layer 606 providedtherebetween functions as the capacitor 108.

In addition, in the optical shutter region in FIGS. 7A and 7B, aninsulating layer 609 is formed between the conductive layer 603 and thegate insulating layer 606. Further, a spacer 610 is formed over theelectrode 605 in a portion where the electrode 605 and the insulatinglayer 609 overlap with each other.

FIG. 7A is a top view of the optical shutter region provided with thespacer 610. In FIG. 7B, a substrate 614 is provided to face thesubstrate 600 provided with the spacer 610.

A liquid crystal layer 616 containing a liquid crystal is providedbetween the substrate 614 and the electrodes 605 and 608. The liquidcrystal element 106 is formed in a region including the electrode 605,the electrode 608, and the liquid crystal layer 616.

Polarizing plates (not illustrated) are provided outside the substrate600 and the substrate 614.

The electrode 605 and the electrode 608 can be formed using alight-transmitting conductive material such as indium tin oxidecontaining silicon oxide (ITSO), indium tin oxide (ITO), zinc oxide(ZnO), indium zinc oxide, or zinc oxide to which gallium is added (GZO),for example.

Injection of liquid crystals for formation of the liquid crystal layer616 may be performed by a dispenser method (a dripping method) or adipping method (a pumping method).

Note that the substrate 614 may be provided with a light-blocking filmcapable of blocking light so that disclination caused by disorder ofalignment of the liquid crystal between optical shutter regions isprevented from being observed or dispersed light is prevented fromentering a plurality of adjacent optical shutter regions. Thelight-blocking film can be formed using an organic resin containing ablack pigment such as a carbon black or low-valent titanium oxide.Alternatively, the light-blocking film can be formed using a filmincluding chromium.

THIRD SPECIFIC EXAMPLE OF LIGHT-BLOCKING PANEL 20

A specific example of the light-blocking panel 20 that is different fromthe specific examples of the light-blocking panel 20 in FIGS. 6A and 6Band FIGS. 7A and 7B is described with reference to FIG. 18.Specifically, an example of a light-blocking panel provided with anoptical shutter region that does not include the switches included inthe optical shutter regions in FIGS. 6A and 6B and FIGS. 7A and 7B isdescribed. In the optical shutter region in FIG. 18, electrodes 702 (anelectrode 702 a, an electrode 702 b, and an electrode 702 c) processedinto a stripe pattern and electrodes 712 (an electrode 712 a, anelectrode 712 b, and an electrode 712 c) processed into a stripe patternare stacked in a lattice pattern. When the electrodes overlap with eachother in a lattice pattern with a liquid crystal provided therebetween,a liquid crystal element can be formed in a dotted pattern. Thus, alight-blocking region or a light-transmitting region can be controlledwith higher accuracy.

EXAMPLE 1

The display device according to one embodiment of the present inventioncan be used for display devices, laptops, or image reproducing devicesprovided with recording media (typically, devices which reproduce thecontent of recording media such as digital versatile discs (DVDs) andhave displays for displaying the reproduced images). Further, aselectronic devices which can include the display device according to oneembodiment of the present invention, cellular phones, portable gamemachines, personal digital assistants, e-book readers, cameras such asvideo cameras and digital still cameras, goggle-type displays (headmounted displays), navigation systems, audio reproducing devices (e.g.,car audio systems and digital audio players), copiers, facsimiles,printers, multifunction printers, automated teller machines (ATM),vending machines, and the like can be given. In this example, specificexamples of these electronic devices are described with reference toFIGS. 8A to 8C.

FIG. 8A illustrates a portable game machine, which includes a housing5001, a housing 5002, a display portion 5003, a display portion 5004, amicrophone 5005, speakers 5006, an operation key 5007, a stylus 5008,and the like. The display device according to one embodiment of thepresent invention can be used as the display portion 5003 or the displayportion 5004. It is possible to provide a portable game machine capableof displaying a partial 3D image when the display device according toone embodiment of the present invention is used as the display portion5003 or the display portion 5004. Note that although the portable gamemachine in FIG. 8A has the two display portions 5003 and 5004, thenumber of display portions included in the portable game machine is notlimited thereto.

FIG. 8B illustrates a laptop, which includes a housing 5201, a displayportion 5202, a keyboard 5203, a pointing device 5204, and the like. Thedisplay device according to one embodiment of the present invention canbe used as the display portion 5202. It is possible to provide a laptopcapable of displaying a partial 3D image when the display deviceaccording to one embodiment of the present invention is used as thedisplay portion 5202.

FIG. 8C illustrates a personal digital assistant, which includes ahousing 5401, a display portion 5402, operation keys 5403, and the like.The display device according to one embodiment of the present inventioncan be used as the display portion 5402. It is possible to provide apersonal digital assistant capable of displaying a partial 3D image whenthe display device according to one embodiment of the present inventionis used as the display portion 5402.

EXAMPLE 2

The display device according to one embodiment of the present inventioncan display both a 3D image and a 2D image when drive is controlled ineach of the plurality of pixel regions 100 included in the display panel10 and in each of the optical shutter regions 200 included in thelight-blocking panel 20. Here, drive frequency needed for the displaypanel 10 and drive frequency needed for the light-blocking panel 20 aredifferent from each other. In other words, the display panel 10 needs tobe constantly driven in order to display a moving image, and thelight-blocking panel 20 needs to be regularly or irregularly driven inaccordance with switching of 3D display and 2D display. In that case, aperiod during which the light-blocking panel 20 needs to be driven ismuch shorter than a period during which the light-blocking panel 20 iskept in a certain state. In this example, operation to drive thelight-blocking panel 20 only in a desired period and to keep thelight-blocking panel 20 in a certain state in periods other than theperiod and a structure that is suitable for the operation are describedwith reference to FIGS. 9A to 9D. Note that by the operation, the powerconsumption of the display device can be reduced.

FIG. 9A illustrates a structure example of the display device in thisexample. The display device in FIG. 9A includes the display panel 10including the plurality of pixel regions 100 arranged in matrix, thelight-blocking panel 20 including the plurality of optical shutterregions 200 arranged in matrix, and a controller 30 for controlling theoperation of the display panel 10 and the light-blocking panel 20. Notethat a display panel or the like that includes the pixel regions inFIGS. 4A to 4C and FIGS. 5A and 5B can be used as the display panel 10,and a light-blocking panel or the like that includes the optical shutterregions in FIGS. 6A and 6B and FIGS. 7A and 7B can be used as thelight-blocking panel 20. Further, the controller 30 has a function ofcontrolling display of a 3D or 2D moving image in the display panel 10and a function of driving the light-blocking panel 20 only in a desiredperiod and keeping the state of the light-blocking panel 20 in periodsother than the period.

FIG. 9B is an equivalent circuit diagram of the optical shutter region200 included in the light-blocking panel 20 in FIGS. 6A and 6B and FIGS.7A and 7B. Specifically, the optical shutter region 200 in FIG. 9Bincludes the transistor 107, the liquid crystal element 106 to which asignal is input through the transistor 107, and the capacitor 108 forholding the potential of the signal. In the optical shutter region 200,whether to transmit light is selected by control of alignment of aliquid crystal of the liquid crystal element in accordance with thepotential of the signal. Thus, in order to perform the above operation,it is necessary to hold the potential of the signal for a long time. Inorder to meet the need, a channel region of the transistor 107 ispreferably formed using an oxide semiconductor. This is because leakageof electric charge through the transistor 107 can be reduced, so that afluctuation in the potential of the signal can be suppressed.

An oxide semiconductor has a wider band gap and lower intrinsic carrierdensity than silicon. Thus, with the use of an oxide semiconductor forthe semiconductor layer of the transistor 107, a transistor that hasmuch lower off-state current than a transistor including a normalsemiconductor such as silicon or germanium can be formed.

Note that a highly-purified oxide semiconductor (a purified oxidesemiconductor) obtained by reduction of impurities such as moisture orhydrogen which serve as electron donors (donors) is an intrinsic(i-type) semiconductor or a substantially intrinsic semiconductor. Thus,a transistor including the oxide semiconductor has extremely lowoff-state current. Specifically, the concentration of hydrogen in thehighly-purified oxide semiconductor that is measured by secondary ionmass spectroscopy (SIMS) is 5×10¹⁹/cm³ or lower, preferably 5×10¹⁸/cm³or lower, more preferably 5×10¹⁷/cm³ or lower, still more preferably1×10¹⁶/cm³ or lower. In addition, the carrier density of the oxidesemiconductor that can be measured by Hall effect measurement is lowerthan 1×10¹⁴/cm³, preferably lower than 1×10¹²/cm³, more preferably lowerthan 1×10¹¹/cm³. Further, the band gap of the oxide semiconductor is 2eV or more, preferably 2.5 eV or more, more preferably 3 eV or more.With the use of an oxide semiconductor film which is highly purified bya sufficient decrease in the concentration of impurities such asmoisture or hydrogen, the off-state current value of the transistor canbe decreased. Various experiments can prove the low off-state current ofthe transistor including the highly-purified oxide semiconductor film asan active layer. For example, even with an element with a channel widthof 1×10⁶ μm and a channel length of 10 μm, in a range of 1 to 10 V ofvoltage (drain voltage) between a source terminal and a drain terminal,off-state current can be lower than or equal to the measurement limit ofa semiconductor parameter analyzer, that is, lower than or equal to1×10⁻¹³ A. In that case, it can be seen that off-state current densitycorresponding to a value obtained by division of the off-state currentby the channel width of the transistor is lower than or equal to 100zM/μm.

The analysis of the concentration of hydrogen in the oxide semiconductorfilm is described here. The concentration of hydrogen in thesemiconductor film and the conductive film is measured by secondary ionmass spectroscopy (SIMS). It is known that it is difficult to obtainprecise data in the vicinity of a surface of a sample or in the vicinityof an interface between stacked films formed using different materialsby a SIMS analysis in principle. Thus, in the case where thedistribution of the concentration of hydrogen in the film in a thicknessdirection is analyzed by SIMS, an average value in a region of the filmin which the value is not greatly changed and substantially the samevalue can be obtained is employed as the hydrogen concentration. Inaddition, in the case where the thickness of the film is small, a regionwhere substantially the same value can be obtained cannot be found insome cases due to the influence of the hydrogen concentration of thefilms adjacent to each other. In that case, the maximum value or theminimum value of the hydrogen concentration in the region of the film isemployed as the hydrogen concentration of the film. Further, in the casewhere a mountain-shaped peak having the maximum value or a valley-shapedpeak having the minimum value do not exist in the region of the film,the value at an inflection point is employed as the hydrogenconcentration.

Note that a four-component metal oxide such as an In—Sn—Ga—Zn—O-basedoxide semiconductor; a three-component metal oxide such as anIn—Ga—Zn—O-based oxide semiconductor, an In—Sn—Zn—O-based oxidesemiconductor, an In—Al—Zn—O-based oxide semiconductor, aSn—Ga—Zn—O-based oxide semiconductor, an Al—Ga—Zn—O-based oxidesemiconductor, or a Sn—Al—Zn—O-based oxide semiconductor; atwo-component metal oxide such as an In—Zn—O-based oxide semiconductor,a Sn—Zn—O-based oxide semiconductor, an Al—Zn—O-based oxidesemiconductor, a Zn—Mg—O-based oxide semiconductor, a Sn—Mg—O-basedoxide semiconductor, an In—Mg—O-based oxide semiconductor, or anIn—Ga—O-based oxide semiconductor; an In—O-based oxide semiconductor; aSn—O-based oxide semiconductor; a Zn—O-based oxide semiconductor; or thelike can be used as the oxide semiconductor. In this specification, forexample, an In—Sn—Ga—Zn—O-based oxide semiconductor is a metal oxidecontaining indium (In), tin (Sn), gallium (Ga), and zinc (Zn), and thereis no particular limitation on the stoichiometric proportion thereof.The oxide semiconductor may contain silicon.

The oxide semiconductor can be represented by a chemical formula,InMO₃(ZnO)_(m) (m>0, m is not necessarily a natural number). Here, Mrepresents one or more metal elements selected from Ga, Al, Mn, or Co.

In the case where an In—Zn—O-based material is used for the oxidesemiconductor, a target used has a composition ratio of In:Zn=50:1 to1:2 in an atomic ratio (In₂O₃:ZnO=25:1 to 1:4 in a molar ratio),preferably In:Zn=20:1 to 1:1 in an atomic ratio (In₂O₃:ZnO=10:1 to 1:2in a molar ratio), more preferably In:Zn=1.5:1 to 15:1 in an atomicratio (In₂O₃:ZnO=3:4 to 15:2 in a molar ratio). For example, when atarget used for deposition of an In—Zn—O-based oxide semiconductor has acomposition ratio of In:Zn:O=X:Y:Z in an atomic ratio, where Z>1.5X+Y.

Note that the oxide semiconductor may be either amorphous orcrystalline. For example, a CAAC-OS (c-axis aligned crystalline oxidesemiconductor) film can be used as the oxide semiconductor film.

The CAAC-OS film is not completely single crystal nor completelyamorphous. The CAAC-OS film is an oxide semiconductor film with acrystal-amorphous mixed phase structure where crystal parts are includedin an amorphous phase. Note that in most cases, the crystal part fitsinside a cube whose one side is less than 100 nm From an observationimage obtained with a transmission electron microscope (TEM), a boundarybetween the amorphous part and a crystal part in the CAAC-oxidesemiconductor film is not clear. Further, with the TEM, a grain boundaryin the CAAC-oxide semiconductor film is not found. Thus, in the CAAC-OSfilm, a reduction in electron mobility, due to the grain boundary, issuppressed.

In each of the crystal parts included in the CAAC-OS film, a c-axis isaligned in a direction parallel to a normal vector of a surface wherethe CAAC-OS film is formed or a normal vector of a surface of theCAAC-OS film, triangular or hexagonal atomic order which is seen fromthe direction perpendicular to the a-b plane is formed, and metal atomsare arranged in a layered manner or metal atoms and oxygen atoms arearranged in a layered manner when seen from the direction perpendicularto the c-axis. Note that, among crystal parts, the directions of thea-axis and the b-axis of one crystal part may be different from those ofanother crystal part. In this specification, a simple term“perpendicular” includes a range from 85 to 95°. In addition, a simpleterm “parallel” includes a range from −5 to 5°.

In the CAAC-OS film, distribution of crystal parts is not necessarilyuniform. For example, in the formation process of the CAAC-OS film, inthe case where an oxide semiconductor film is formed on one surface andcrystal growth occurs from a surface side of the oxide semiconductorfilm, the proportion of crystal parts in the vicinity of the surface ofthe CAAC-OS film is higher than that in the vicinity of the surfacewhere the CAAC-OS film is formed in some cases. Further, when animpurity is added to the CAAC-OS film, the crystal part in a region towhich the impurity is added becomes amorphous in some cases.

Since the c-axes of the crystal parts included in the CAAC-OS film arealigned in the direction parallel to a normal vector of a surface wherethe CAAC-OS film is formed or a normal vector of a surface of theCAAC-OS film, the directions of the c-axes may be different from eachother depending on the shape of the CAAC-OS film (the cross-sectionalshape of the surface where the CAAC-OS film is formed or thecross-sectional shape of the surface of the CAAC-OS film). Note thatwhen the CAAC-OS film is formed, the direction of c-axis of the crystalpart is the direction parallel to a normal direction (vector) of thesurface where the CAAC-OS film is formed or a normal direction (vector)of the surface of the CAAC-OS film. The crystal part is formed bydeposition or by performing treatment for crystallization such as heattreatment after deposition.

With use of the CAAC-OS film in a transistor, a change in electricalcharacteristics of the transistor due to irradiation with visible lightor ultraviolet light can be reduced. Thus, the transistor has highreliability.

FIGS. 9C and 9D are flow charts each illustrating an operation exampleof the controller 30 in FIG. 9A. Specifically, FIG. 9C is a flow chartillustrating an operation example of the controller 30 for controllingthe display panel 10, and FIG. 9D is a flow chart illustrating anoperation example of the controller 30 for controlling thelight-blocking panel 20.

After the controller 30 starts to operate, a display control signal isoutput to the display panel 10. Here, the display control signal is animage signal input to each of the plurality of pixel regions 100arranged in matrix, a signal (e.g., a clock signal) for controllingoperation, or the like. The display control signal is constantlysupplied to the display panel 10 as long as the controller 30 continuesdisplay in the display panel 10.

Further, in the case where the controller 30 operates and 3D display isperformed in part or the whole of display in the display device, thecontroller 30 outputs a light-blocking control signal to thelight-blocking panel 20. Here, the light-blocking control signal is acontrol signal (a signal for determining whether to block light) inputto each of the plurality of optical shutter regions 200 arranged inmatrix, a signal (e.g., a clock signal) for controlling operation, orthe like. After control signals are supplied to the plurality of opticalshutter regions 200, supply of light-blocking control signals isstopped. Note that in the case where a region in which 3D display isperformed is changed, the controller 30 outputs a light-blocking controlsignal to the light-blocking panel 20 again. In this manner, thelight-blocking control signal is regularly or irregularly supplied tothe light-blocking panel 20 when 3D display is performed or a region inwhich 3D display is performed is changed.

Note that in the flow chart in FIG. 9D, in the case where thelight-blocking control signal is not supplied to the light-blockingpanel 20 for a long time, a light-blocking control signal for performing3D display in one region can be supplied (refreshed) to thelight-blocking panel 20 again. In other words, in the case where 3Ddisplay is performed in a specific region of the display device for along time, a light-blocking control signal for performing 3D display canbe supplied to the light-blocking panel 20 as appropriate (regularly orirregularly) in the specific region.

By the operation in this example, it is not necessary to constantlydrive the light-blocking panel 20; thus, the power consumption of thedisplay device can be reduced.

EXAMPLE 3

Note that in order to display a 3D image as described above, it isnecessary that the plurality of optical shutter regions be different inpositional relation between the optical shutter region and thecorresponding two pixel regions or that the positional relation betweenan optical shutter region included in a specific region andcorresponding two pixel regions be different from the positionalrelation between an optical shutter region included in a region otherthan the specific region and corresponding two pixel regions, though thepositional relation between the optical shutter region included in thespecific region and the corresponding two pixel regions is common Inthis example, how these positional relations are different in thedisplay device is described giving a specific example.

FIG. 10 illustrates the structure of the display device in this example.The display device in FIG. 10 includes the 3.9-inch display panel 10whose pixel resolution is WVGA (800×480) and the light-blocking panel 20provided in a direction in which the display panel 10 emits light. Notethat an interval between a plane on which the plurality of pixel regionsincluded in the display panel 10 are provided and a plane on which theplurality of optical shutter regions included in the light-blockingpanel 20 are provided is 0.6 mm Further, each pixel region includes ared pixel (R), a green pixel (G), and a blue pixel (B). The width ofeach pixel region in a lateral direction (a direction in which aparallax between a left eye and a right eye exists) is 0.1 mmFurthermore, the display device is designed so that a user whoseinterval between both eyes is 65 mm can view a 3D image when the user is390 mm away from the display device. Note that in FIG. 10, A indicatesthe positions of two pixel regions provided in front of the left eye 31,B indicates the positions of two pixel regions provided between the lefteye 31 and the right eye 32, and C indicates the positions of two pixelregions provided in front of the right eye 32. Here, a pixel regionpositioned in a column at an end of the pixel is placed in front of theleft eye 31 or the right eye 32. In the following description, thedisplay device displays a 3D image across the front of the screen.

FIG. 11A illustrates the positional relation between two pixel regionsA100_(—)1 and A100_(—)2 positioned in front of the left eye 31 andoptical shutter regions A200_(—)1 and A200_(—)2 positioned in front ofthe pixel regions A100_(—)1 and A100_(—)2. Here, the pixel regionA100_(—)1 is viewed by the right eye 32, but is not viewed by the lefteye 31 because it is blocked by the optical shutter region A200_(—)1. Inaddition, the pixel region A100_(—)2 is viewed by the left eye 31, butis not viewed by the right eye 32 because it is blocked by the opticalshutter region A200_(—)2. FIG. 11B illustrates an angle formed by thedirection of the right eye 32 and the vertical line of the display panel10 under the above condition. Under the condition, the angle isapproximately 11°. Note that in FIG. 11B, 1R indicates one of pixelregions in a first column where a 3D image for the right eye isdisplayed, 1L indicates one of pixel regions in the first column where a3D image for the left eye is displayed, 2R to 4R indicate pixel regionsin second to fourth columns where 3D images for the right eye aredisplayed, and 2L to 4L indicate pixel regions in the second to fourthcolumns where 3D images for the left eye are displayed.

FIG. 12A illustrates the positional relation between two pixel regionsB100_(—)1 and B100_(—)2 positioned between the left eye 31 and the righteye 32 and optical shutter regions B200_(—)1 and B200_(—)2 positioned infront of the pixel regions B100_(—)1 and B100_(—)2. Here, the pixelregion B100_(—)1 is viewed by the right eye 32, but is not viewed by theleft eye 31 because it is blocked by the optical shutter regionB200_(—)1. In addition, the pixel region B100_(—)2 is viewed by the lefteye 31, but is not viewed by the right eye 32 because it is blocked bythe optical shutter region B200_(—)2. FIG. 12B illustrates an angleformed by the direction of the right eye 32 and the vertical line of thedisplay panel 10 under the above condition. Under the condition, theangle is approximately 5°. Note that in FIG. 12B, 199R to 202R and 198Lto 201L are similar to 1R to 4R and 1L to 4L in FIG. 11A, respectively.

FIG. 13A illustrates the positional relation between two pixel regionsC100_(—)1 and C100_(—)2 positioned in front of the right eye 32 andoptical shutter regions C200_(—)1 and C200_(—)2 positioned in front ofthe pixel regions C100_(—)1 and C100_(—)2. Here, the pixel regionC100_(—)1 is viewed by the right eye 32, but is not viewed by the lefteye 31 because it is blocked by the optical shutter region C200_(—)1. Inaddition, the pixel region C100_(—)2 is viewed by the left eye 31, butis not viewed by the right eye 32 because it is blocked by the opticalshutter region C200_(—)2. FIG. 13B illustrates an angle formed by thedirection of the left eye 31 and the vertical line of the display panel10 under the above condition. Under the condition, the angle isapproximately 11°. Note that in FIG. 12B, 397R to 400R and to 400L aresimilar to 1R to 4R and 1L to 4L in FIG. 11A, respectively.

EXAMPLE 4

In the display device, it is assumed that the direction of the user'seye is positioned in the center of the screen; however, the direction ofthe user's eye is not necessarily positioned in the center of thescreen. Further, even when 3D images are displayed in two regions of thescreen, the user does not necessarily focus on the images at the sametime. In this example, a display device for selecting a region in whicha 3D image is displayed in accordance with the direction of the user'seye is specifically described.

FIG. 14 illustrates a display device in this example. The display devicein FIG. 14 includes a screen 1000 on which 3D images are displayed in aregion 1001 and a region 1002 and 2D images are displayed in regionsother than the region 1001 and the region 1002, and a viewer sensor 2000capable of detecting the direction of the user's eye that is positionedaround the screen 1000. Further, the display device can control theoperation of a plurality of optical shutter regions included in alight-blocking panel in accordance with the direction of the user's eye.

Specifically, when the viewer sensor 2000 decides that the user sees a3D image in the region 1001, the display device controls the operationso that light is blocked in the plurality of optical shutter regionsthat correspond to the region 1001 among the plurality of opticalshutter regions included in the light-blocking panel. Further, whenviewer sensor 2000 decides that the user cannot sees a 3D image in theregion 1002, a 3D image is not displayed in the region 1002. In otherwords, the display device controls the operation so that light istransmitted in the plurality of optical shutter regions that correspondto the region 1002 among the plurality of optical shutter regionsincluded in the light-blocking panel (see FIG. 15). Note that in FIG.15, R indicates a pixel region where a 3D image for the right eye isdisplayed, L indicates a pixel region where a 3D image for the left eyeis displayed, and a gray portion indicates an optical shutter regionwhere light is blocked (the same can be said for FIG. 16 and FIG. 17).

Similarly, when the viewer sensor 2000 decides that the user sees a 3Dimage in the region 1002, the display device controls the operation sothat light is blocked in the plurality of optical shutter regions thatcorrespond to the region 1002 among the plurality of optical shutterregions included in the light-blocking panel. Further, when viewersensor 2000 decides that the user cannot sees a 3D image in the region1001, a 3D image is not displayed in the region 1001. In other words,the display device controls the operation so that light is transmittedin the plurality of optical shutter regions that correspond to theregion 1001 among the plurality of optical shutter regions included inthe light-blocking panel (see FIG. 16).

Further, when the viewer sensor 2000 decides that the user can see 3Dimages both in the region 1001 and the region 1002, the display devicecontrols the operation so that light is blocked in the plurality ofoptical shutter regions that correspond to the region 1001 and theregion 1002 among the plurality of optical shutter regions included inthe light-blocking panel (see FIG. 17).

When the operation of the plurality of optical shutter regions includedin the light-blocking panel is controlled in consideration of thedirection of the user's eye in this manner, an optimal barrier for 3Ddisplay can be formed.

EXPLANATION OF REFERENCES

10: display panel, 20: light-blocking panel, 20 a: region, 30:controller, 31: left eye, 32: right eye, 100: pixel region, 100 a: pixelregion, 100 b: pixel region, 100 c: pixel region, 100 d: pixel region,106: liquid crystal element, 107: transistor, 108: capacitor, 200:optical shutter region, 200 a: optical shutter region, 200 b: opticalshutter region, 201: substrate, 202: gate 30 electrode layer, 204: gateinsulating layer, 206: semiconductor layer, 208: drain electrode layer,210: insulating layer, 212: insulating layer, 214: reflective electrodelayer, 216: partition, 218: light-emitting layer, 219: transflectiveelectrode layer, 220 a: transparent electrode layer, 220 b: transparentelectrode layer, 230: transistor, 240 a: blue pixel, 240 b: green pixel,240 c: red pixel, 251: substrate, 252: light-blocking film, 254: colorfilter, 256: overcoat, 260: space, 300: substrate, 310: insulatinglayer, 312: partition, 314: electrode, 316: light-emitting layer, 318:electrode, 320: light-emitting element, 322: space, 330: transistor,350: substrate, 352: light-blocking film, 354: color filter, 356:overcoat, 500: substrate, 501: conductive layer, 502: conductive layer,503: conductive layer, 504: conductive layer, 505: electrode, 506: gateinsulating layer, 507: semiconductor layer, 510: spacer, 512: insulatinglayer, 513: insulating layer, 514: substrate, 515: electrode, 516:liquid crystal layer, 517: light-blocking film, 520: semiconductorlayer, 521: conductive layer, 523: semiconductor layer, 600: substrate,601: conductive layer, 602: conductive layer, 603: conductive layer,604: conductive layer, 605: electrode, 606: gate insulating layer, 607:semiconductor layer, 608: electrode, 609: insulating layer, 610: spacer,612: insulating layer, 613: insulating layer, 614: substrate, 616:liquid crystal layer, 702: electrode, 702 a: electrode, 702 b:electrode, 702 c: electrode, 712: electrode, 712 a: electrode, 712 b:electrode, 712 c: electrode, 1000: screen, 1001: region, 1002: region,2000: viewer sensor, 5001: housing, 5002: housing, 5003: displayportion, 5004: display portion, 5005: microphone, 5006: speaker, 5007:operation key, 5008: stylus, 5201: housing, 5202: display portion, 5203:keyboard, 5204: pointing device, 5401: housing, 5402: display portion,5403: operation key, A100_(—)1: pixel region, A100_(—)2: pixel region,A200_(—)1: optical shutter region, A200_(—)2: optical shutter region,B100_(—)1: pixel region, B100_(—)2: pixel region, B200_(—)1: opticalshutter region, B200_(—)2: optical shutter region, C100_(—)1: pixelregion, C100_(—)2: pixel region, C200_(—)1: optical shutter region, andC200_(—)2: optical shutter region.

This application is based on Japanese Patent Application serial No.2011-029203 filed with Japan Patent Office on Feb. 14, 2011, JapanesePatent Application serial No. 2011-030566 filed with Japan Patent Officeon Feb. 16, 2011, and Japanese Patent Application serial No. 2011-133336filed with Japan Patent Office on Jun. 15, 2011, the entire contents ofwhich are hereby incorporated by reference.

1. (canceled)
 2. A display device comprising: a display panel comprisingpixel regions; and a light-blocking panel comprising optical shutterregions each comprising: a transistor; and a liquid crystal element,wherein a channel region of the transistor comprises an oxidesemiconductor, wherein light transmission of the liquid crystal elementis selected depending on a signal input through the transistor, andwherein the light-blocking panel is provided in a direction in whichlight is emitted from the display panel.
 3. The display device accordingto claim 2, wherein a concentration of hydrogen in the oxidesemiconductor is 5×10¹⁹/cm³ or lower.
 4. The display device according toclaim 2, wherein a carrier density of the oxide semiconductor is lowerthan 1×10¹⁴/cm³.
 5. The display device according to claim 2, wherein aband gap of the oxide semiconductor is 2 eV or more.
 6. The displaydevice according to claim 2, wherein a value obtained by division of anoff-state current by a channel width of the transistor is lower than orequal to 100 zA/μm.
 7. The display device according to claim 2, whereincrystal parts comprised in the oxide semiconductor are aligned in adirection substantially perpendicular to a surface of the oxidesemiconductor.
 8. The display device according to claim 2, wherein adistance from one end to an opposing end of all the optical shutterregions is shorter than a distance from one end to an opposing end ofall the pixel regions.
 9. A display device comprising: a display panelcomprising pixel regions; a light-blocking panel comprising opticalshutter regions each comprising: a transistor; and a liquid crystalelement; and a sensor operationally connected to the light-blockingpanel, wherein a channel region of the transistor comprises an oxidesemiconductor, wherein light transmission of the liquid crystal elementis selected depending on a signal input through the transistor, andwherein the light-blocking panel is provided in a direction in whichlight is emitted from the display panel.
 10. The display deviceaccording to claim 9, wherein a concentration of hydrogen in the oxidesemiconductor is 5×10¹⁹/cm³ or lower.
 11. The display device accordingto claim 9, wherein a carrier density of the oxide semiconductor islower than 1×10¹⁴/cm³.
 12. The display device according to claim 9,wherein a band gap of the oxide semiconductor is 2 eV or more.
 13. Thedisplay device according to claim 9, wherein a value obtained bydivision of an off-state current by a channel width of the transistor islower than or equal to 100 zA/μm.
 14. The display device according toclaim 9, wherein crystal parts comprised in the oxide semiconductor arealigned in a direction substantially perpendicular to a surface of theoxide semiconductor.
 15. The display device according to claim 9,wherein a distance from one end to an opposing end of all the opticalshutter regions is shorter than a distance from one end to an opposingend of all the pixel regions.
 16. The display device according to claim9, wherein the sensor is configured to detect a direction of a user'seyes.
 17. The display device according to claim 16, wherein operation ofthe optical shutter regions is controlled in accordance with thedirection of the user's eyes.
 18. A display device comprising: a displaypanel comprising pixel regions; and a light-blocking panel comprisingoptical shutter regions each comprising: a transistor; and a liquidcrystal element, wherein a channel region of the transistor comprises anoxide semiconductor, wherein one of a source and a drain of thetransistor is electrically connected to a first electrode of the liquidcrystal element, and wherein the light-blocking panel is provided in adirection in which light is emitted from the display panel.
 19. Thedisplay device according to claim 18, wherein a concentration ofhydrogen in the oxide semiconductor is 5×10¹⁹/cm³ or lower.
 20. Thedisplay device according to claim 18, wherein a carrier density of theoxide semiconductor is lower than 1×10¹⁴/cm³.
 21. The display deviceaccording to claim 18, wherein a band gap of the oxide semiconductor is2 eV or more.
 22. The display device according to claim 18, wherein avalue obtained by division of an off-state current by a channel width ofthe transistor is lower than or equal to 100 zA/μm.
 23. The displaydevice according to claim 18, wherein crystal parts comprised in theoxide semiconductor are aligned in a direction substantiallyperpendicular to a surface of the oxide semiconductor.
 24. The displaydevice according to claim 18, wherein a distance from one end to anopposing end of all the optical shutter regions is shorter than adistance from one end to an opposing end of all the pixel regions. 25.The display device according to claim 18, wherein the optical shutterregions each comprises: a capacitor electrically connected to thetransistor and the liquid crystal element; and a spacer overlapping withthe first electrode and the capacitor.
 26. The display device accordingto claim 18, wherein the optical shutter regions each comprises: acapacitor electrically connected to the transistor and the liquidcrystal element, the capacitor comprising a second electrode and a firstinsulating layer; a second insulating layer between the first electrodeand the second electrode in a region between the transistor and thecapacitor; and a spacer overlapping with the first electrode, the secondelectrode, the first insulating layer, and the second insulating layer.27. The display device according to claim 18, wherein a part of a firstconductive layer is capable of being the other of the source and thedrain of the transistor, wherein a part of a second conductive layer iscapable of being a gate of the transistor, wherein the first conductivelayer and the second conductive layer overlap with each other in a firstregion and do not overlap with each other in a second region, wherein awidth of the first conductive layer in the first region is smaller thana width of the first conductive layer in the second region.
 28. Thedisplay device according to claim 18, wherein a part of a firstconductive layer is capable of being the other of the source and thedrain of the transistor, wherein a part of a second conductive layer iscapable of being a gate of the transistor, wherein the first conductivelayer and the second conductive layer overlap with each other in a firstregion and do not overlap with each other in a second region, wherein asemiconductor layer is interposed between the first conductive layer andthe second conductive layer in the first region.